Remove Perspective Distortion

For a human observer, closer objects seem to be bigger than the same objects in a farther position (related to the observer). The observer has the impression that a long pipe, as looked at from one of its extremes, seems to be decreasing in diameter as the observer looks farther along the pipe.

This is known as Perspective Effect (see following figure) or in terms of 3D acquisition, Perspective Distortion.

The following pictures show an example of the reconstruction of a tilted cylinder using proportional reconstruction and using SAL3D Metric reconstruction. The proportional reconstruction assumes a constant ratio between pixels and metric units, but, due to perspective distortion, this assumption is not true.

Proportional cylinder reconstruction. a) Range Map; b) COP; c) ZMap

SAL3D Metric cylinder reconstruction. a) Range Map; b) COP; c) ZMap

Observing the cloud of points and also the ZMap obtained in both situations, it is clear that the proportional reconstruction distorts the object, while the SAL3D Metric reconstruction preserves the original shape.